The present invention relates to a developer solution for a photoresist layer used in photolithographic patterning. More particularly, the invention relates to a novel aqueous alkaline developer solution for a photoresist layer on a metallic substrate surface capable of exhibiting an excellent anti-corrosive effect to the metallic surface and causing no troubles of exfoliation of the upper metallic layer from the substrate surface which is laminated with an overlayer of a metal of different kind from the metal of the substrate so as to be useful in the manufacturing process of various kinds of semiconductor devices and liquid crystal display panels.
The method of photolithographic patterning is a well established technology in the manufacturing process of various kinds of semiconductor devices and liquid crystal display panels in which the etching treatment or diffusion treatment is preceded, with an object to selectively protect the substrate surface against the treatment, by coating of the substrate surface with a photosensitive resist composition to form a photoresist layer which is pattern-wise exposed to actinic rays such as ultraviolet light, deep ultraviolet light, excimer laser beams, X-rays and electron beams followed by a development treatment of the resist layer to pattern-wise dissolve away the resist layer.
The developer solution used in the above mentioned development treatment of the photoresist layer is usually an aqueous alkaline solution containing a water-soluble organic base free from metallic constituents which are detrimental against performance of the semiconductor devices or liquid crystal display panels. Examples of such a metal-free organic base include tetramethylammonium hydroxide disclosed in IBM Technical Disclosure Bulletin, volume 3, No. 7, page 2009 (1970) and trimethyl(2-hydroxyethyl)ammonium hydroxide disclosed in U.S. Pat. No. 4,238,661.
Proposals and attempts have been made heretofore to admix the above mentioned organic base-containing aqueous developer solution with various kinds of additives with an object to improve the developability of the developer solution. For example, Japanese Patent Kokai 58-9143 teaches admixture of a specific quaternary ammonium compound which serves as a surface active agent. Japanese Patent Kokai 64-19344 discloses an aqueous developer solution containing from 0.2 to 3.5% by weight of tetramethylammonium hydroxide and from 0.2 to 10% by weight of a polyhydric alcohol, the balance being water. Such an aqueous developer solution is widely employed as a general-purpose developer solution by virtue of easiness in storage and waste disposal along with safety from fire hazards.
It is sometimes the case that the substrate used in the manufacture of semiconductor devices and liquid crystal display panels is a silicon wafer or a glass plate provided on the surface with a layer of a metal such as aluminum to serve as the electric circuit pattern. When such a substrate having a metallic layer is subjected to the photolithographic patterning process to form a patterned metallic layer, a trouble is sometimes encountered that the aqueous alkaline developer solution attacks the metallic layer to cause corrosion of the metallic layer. A recently highlighted substrate as a display for a thin-film transistor (TFT) is a glass plate which is provided with a transparent electroconductive film of indium oxide or mixed oxide of indium and tin called ITO and, further thereon, with a vapor-deposited aluminum film as an electroconductive layer which is patterned photolithographically. When the development treatment is undertaken for a substrate having a layered structure of different kinds of metals by using a conventional aqueous alkaline developer solution, troubles are sometimes unavoidable that exfoliation of the aluminum film takes place or the aluminum film is partly lifted off the underlying transparent electroconductive film by the gas evolved at the interface of the layers eventually to cause bursting of the aluminum film. It is eagerly desired accordingly to develop a novel aqueous developer solution free from these problems and disadvantages.